C# Online Compiler | .NET Fiddle

using System;
using System.Collections.Generic;
using System.Linq;
					
public class Program
{
	public static void Main()
	{
		List<Observation> observations = new List<Observation>
		{
			new Observation { ID = 1, Location = "CityA", ObservationDate = new DateTime(2023, 01, 15), Temperature = 10, Precipitation = 5 },
			new Observation { ID = 2, Location = "CityA", ObservationDate = new DateTime(2023, 01, 16), Temperature = 12, Precipitation = 7 },
			new Observation { ID = 3, Location = "CityB", ObservationDate = new DateTime(2023, 02, 15), Temperature = 15, Precipitation = 4 },
			new Observation { ID = 4, Location = "CityB", ObservationDate = new DateTime(2023, 02, 16), Temperature = 17, Precipitation = 2 }
			// Add more observations as needed
		};
		
		// Step 1: Calculate average temperature and total precipitation for each location for each month
		var monthlyStats = observations
			.GroupBy(o => new { o.Location, Month = o.ObservationDate.Month })
			.Select(g => new
			{
				Location = g.Key.Location,
				Month = g.Key.Month,
				AverageTemperature = g.Average(o => o.Temperature),
				TotalPrecipitation = g.Sum(o => o.Precipitation)
			})
			.ToList();

		monthlyStats.ForEach(ms => Console.WriteLine($"Location: {ms.Location}, Month: {ms.Month}, Avg Temp: {ms.AverageTemperature}, Total Precip: {ms.TotalPrecipitation}"));

		// Step 2: Identify the month with the highest average temperature for each location
		var highestAvgTempByLocation = monthlyStats
			.GroupBy(ms => ms.Location)
			.Select(g => new
			{
				Location = g.Key,
				HighestAvgTempMonth = g.OrderByDescending(ms => ms.AverageTemperature).First().Month
			})
			.ToList();

		highestAvgTempByLocation.ForEach(loc => Console.WriteLine($"Location: {loc.Location}, Month with Highest Avg Temp: {loc.HighestAvgTempMonth}"));

		// Step 3: For each location, find the month with the highest total precipitation
		var highestPrecipitationByLocation = monthlyStats
			.GroupBy(ms => ms.Location)
			.Select(g => new
			{
				Location = g.Key,
				HighestPrecipMonth = g.OrderByDescending(ms => ms.TotalPrecipitation).First().Month
			})
			.ToList();

		highestPrecipitationByLocation.ForEach(loc => Console.WriteLine($"Location: {loc.Location}, Month with Highest Precipitation: {loc.HighestPrecipMonth}"));

	}
}

public class Observation
{
    public int ID { get; set; }
    public string Location { get; set; }
    public DateTime ObservationDate { get; set; }
    public double Temperature { get; set; }
    public double Precipitation { get; set; }
}

 
using System;
using System.Collections.Generic;
using System.Linq;
                    
public class Program
{
    public static void Main()
    {
        List<Observation> observations = new List<Observation>
        {
            new Observation { ID = 1, Location = "CityA", ObservationDate = new DateTime(2023, 01, 15), Temperature = 10, Precipitation = 5 },
            new Observation { ID = 2, Location = "CityA", ObservationDate = new DateTime(2023, 01, 16), Temperature = 12, Precipitation = 7 },
            new Observation { ID = 3, Location = "CityB", ObservationDate = new DateTime(2023, 02, 15), Temperature = 15, Precipitation = 4 },
            new Observation { ID = 4, Location = "CityB", ObservationDate = new DateTime(2023, 02, 16), Temperature = 17, Precipitation = 2 }
            // Add more observations as needed
        };
        
        // Step 1: Calculate average temperature and total precipitation for each location for each month
        var monthlyStats = observations
            .GroupBy(o => new { o.Location, Month = o.ObservationDate.Month })
            .Select(g => new
            {
                Location = g.Key.Location,
                Month = g.Key.Month,